Traditionally winches of all types have employed open loop control systems. The operator initiates a signal and the winch responds. Generally this signal controls the speed of the winch and the direction of rotation of the drum (reel in or reel out). The operator does not have positive knowledge of the forces generated by the winch. Indirect cues are available such as the sounds the winch machinery makes as it is loaded, but it takes a highly trained operator to relate these to loads in the winch cable. A natural feel for the force exerted by a winch is very desirable when winching relatively delicate equipment, such as the recovery of light vehicles or pulling a coaxial cable through a conduit. An unexpected obstruction could result in damage to the equipment being winched or a parted cable.
This invention was conceived to overcome this problem by providing the operator with a force feedback signal proportional to the force the winch exerts on the load. This type of control is termed bilateral, that is, force information signals are reflected in either direction of the control system, i.e. reel-in or reel-out.